A crush of rap music fans pushing toward the stage during Travis Scott’s Astroworld festival in Houston killed at least eight people and injured many more as panic rippled through the packed crowd, officials said on Saturday.

The disaster unfolded at NRG Park at around 9 p.m. on Friday during the headline performance by Scott, a Grammy Award-nominated singer and producer. As some in the sold-out audience of about 50,000 surged toward the stage, people began to fall unconscious, some apparently suffering cardiac arrest or other medical issues, officials told reporters outside the venue. Minutes later the chaos was declared a “mass casualty incident.”

“It happened all at once. It seemed like it just happened … over the course of just a few minutes,” said Houston Police Executive Assistant Chief Larry Satterwhite.

“Within the first 30 seconds of the first song, people began to drown – in other people,” a concert-goer with the Instagram handle “Seannafaith” wrote online. “It got tighter and tighter, impossible to breathe as our lungs were compressed between the bodies of those surrounding us. More people began to scream for help.”

Houston-born Scott said he would support the police as they investigate the incident and wanted to help the community heal.

“I’m absolutely devastated by what took place last night. My prayers go out to the families and all those impacted by what happened at Astroworld Festival,” Scott wrote on Twitter. “Love You All.”

It was not yet clear what caused the disaster. An investigation was underway that is likely to focus on security and safety protocols at the event.

Two weeks ago, organizers of another Houston concert canceled it abruptly after fans pushed through a gate and stormed into a Playboi Carti show being held within the same NRG Park complex.

Astroworld, a two-day music festival that was scheduled to culminate on Saturday, had a similar breech at about 2:30 p.m. Friday and went ahead with the show, according to TV reports.

“I think it’s very important that none of us speculate. Nobody has all the answers tonight,” Houston Police Chief Troy Finner said at a news conference.

In an interview with CNN, Houston Fire Chief Samuel Peña described how the crush of fans quickly overwhelmed the private security hired for the festival’s first day.

Authorities transported about 23 people in serious condition to hospitals, 11 of them critical, Pena told CNN. One of the injured was 10 years old. At least eight people succumbed to their injuries, he said, adding that the death toll could rise.

Organizers and Scott were both cooperating with police.

“We are focused on supporting local officials however we can …,” Astroworld Fest, an event organized by Live Nation Entertainment, said on Twitter. It said it was cancelling the second day of the festival.

Fans in distress

Scott stopped multiple times during his 75-minute performance when he spotted fans in distress near the stage, video posted online showed. He asked security to make sure they were safe. Emergency vehicles, lights and alarms flashing, cut through the audience several times.

“We need somebody to help. Somebody passed out right here,” Scott said, according to video of his set, which included a guest appearance by Canadian rapper Drake. “Security, somebody, jump in here real quick.”

The tragedy harkens back to a 1979 concert by British rock band The Who in which 11 people were killed when fans stampeded into the Riverfront Coliseum in Cincinnati before the event.

A reunification center was set up for families who had not heard from loved ones at the festival, the Houston Fire Department said on Twitter.

Another clip, which Reuters could not immediately verify as authentic, showed police performing CPR on several people even as music blared in the background.

Scott came to fame in the early 2010s for his unique vocal style. Astroworld is also the name of his third studio album released in 2018 to critical acclaim.

Scott and Kylie Jenner, from the famed Kardashian family, have a daughter.